Your examples in (1) are not quite interchangeable. In mathematical terms, you might say that they are equal, but not congruent (or congruent, but not identical). The nuance is difficult to see in that pair of examples, but I'll try to highlight it as best I can.

In 1a, ways of writing is a noun phrase, and can be replaced with a single word or a different phrase without changing the underlying semantic structure of the sentence.

In 1b, though, ways stands alone as a noun and to write is the predicate of a separate clause.

The difference is subtle, I will grant, but it is a difference. Ways to write could not, for instance, be directly replaced with the noun orthographies or the noun phrase writing systems easily, although one can imagine them easily replacing ways of writing in any number of contexts.

Interesting analysis; I just wonder what you mean by this: "In 1b, though, ways stands alone as a noun and to write is the predicate of a separate clause." I don't really see more than one clause; and I find it difficult to see how "to write" can be a predicate. I was taught that "to write" is an attribute of "ways".
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CerberusFeb 19 '11 at 23:53